<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <ul>
        <li>1111</li>
        <li>2</li>
        <li>3</li>
    </ul>
    <script>
        var ul = document.querySelector("ul");
        //复制第一个节点,括号里为空，或者为false时，只复制节点，不复制节点里的内容
        //改为true即可
        var lili = ul.children[0].cloneNode(true);
        //复制的节点的位置
        ul.appendChild(lili)
    </script>
</body>

</html>